IRU1010

5

Rev. 1.7

02/03/03

www.irf.com

Assuming the following specifications:

shown in Figure 5.

The steps for selecting the right package with proper

board area for heatsinking to keep the junction tempera-

ture below 135

8C is given as:

1) Calculate the maximum power dissipation using:

2) Calculate the maximum

3) Select a package from the datasheet with lower

than the one calculated in the previous step.

Selecting TO-252 (D-Pak) with at least 0.5" square

of 0.062" FR4 board using 1 oz. copper has 70

which is lower than the calculated number.

To set the output DC voltage, we need to select R1 and

R2:

4) Assuming R1 = 121

V, 1%:

Select R2 = 154

V, 1%.

Figure 5 - Final Schematic for half of the

GTL+ termination regulator.

Layout Consideration

The output capacitors must be located as close to the

mended to use a section of a layer of the PC board as a

prevent any high frequency oscillation that may result

due to excessive trace inductance.

8C

=

= 75.6

8C/W

135 - 35

1.32

3 (5 - 0.5 - 2.85) = 1.32W

3121 = 154.8V

(

)

(

)

-1

2.85

1.25

-1

IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105

TAC Fax: (310) 252-7903

Visit us at www.irf.com for sales contact information

Data and specifications subject to change without notice. 02/01

2.85V

R1

121

1%

R2

154

1%

5V

C2

22uF

C1

10uF

IRU1010

Adj

D1